1. Field of the Invention
The present invention relates generally to spray formed rapid tools and, more specifically, to a method of making a spray formed rapid tool
2. Description of the Related Art
It is known to make a spray formed rapid tool. In spray forming, a master model of a desired tool is produced using a free form fabrication technique. This master model is then used to create a ceramic pattern which is the reverse of the desired tool to be produced. A ceramic slurry, typically alumina, is poured onto the master model and solidified to form the ceramic pattern. When solidification is complete, the resulting ceramic pattern is put through a series of heat cycles and becomes the receptor onto which metal is sprayed to form a deposit in the shape of the desired tool.
Typically, the spray forming process uses a wire-arc spraying. In wire-arc spraying, electric current is carried by two electrically conductive, consumable wires with an electric arc forming between the wire tips. A high-velocity gas jet blowing from behind the consumable wires strips away the molten metal, which continuously forms as the wires are melted by the electric arc. The high-velocity gas jet breaks up or atomizes the molten metal into finer particles in order to create a fine distribution of molten metal droplets. The atomizing gas then accelerates the droplets away from the wire tips to the ceramic pattern where the molten metal droplets impact the ceramic pattern to incrementally form a deposit in the shape of the desired tool.
The desired tool is then removed from the ceramic pattern. The removal is typically accomplished by cutting off the perimeter of the deposit which a high pressure waterjet, chiseling off the majority of the alumina forming the ceramic pattern and then using a glass bead blaster to remove the residual alumina from the surface of the desired tool. The completed desired tool is then mounted and used to produce parts in conventional stamping, die casting, or molding process.
Although the above process for making a spray formed rapid tool has worked well, it suffers from the disadvantage that it takes a considerable amount of time to remove the ceramic pattern from the thermally sprayed tool. Another disadvantage of the above process is that the ceramic pattern cannot be produced directly from the master model. As a result, the process of making the spray formed rapid tool is relatively time consuming and costly. Therefore, there is a need in the art to produce patterns for a spray formed rapid tool that is less time consuming and costly.